Pernicious Anemia (Encyclopedia of Medicine)
Pernicious anemia is a disease in which the red blood cells are abnormally formed, due to an inability to absorb vitamin B12. True pernicious anemia refers specifically to a disorder of atrophied parietal cells leading to absent intrinsic factor, resulting in an inability to absorb B12.
Vitamin B12, or cobalamin, plays an important role in the development of red blood cells. It is found in significant quantities in liver, meats, milk and milk products, and legumes. During the course of the digestion of foods containing B12, the B12 becomes attached to a substance called intrinsic factor. Intrinsic factor is produced by parietal cells which line the stomach. The B12-intrinsic factor complex then enters the intestine, where the vitamin is absorbed into the bloodstream. In fact, B12 can only be absorbed when it is attached to intrinsic factor.
In pernicious anemia, the parietal cells stop producing intrinsic factor. The intestine is then completely unable to absorb B12. So, the vitamin passes out of the body as waste. Although the body has significant amounts of stored B12, this will eventually be used up. At this point, the symptoms of pernicious anemia will develop.
(The entire section is 1413 words.)
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